Superheterodyne receiver



Feb. 17,'1942. J. HAANTJEs ErAL SUPERHETERODYNE RECEIVER Filed June 1-4,1940 NETWORK To 1. F.

LOCAL osc/LLATOR INVENTRS JOHA HAANTJES Alva mssfs ENT/RE rum/v6 A/vogERN RD?? DJ'LTELLEGEN ATTORNEY.

UNTTED STATE Patented Feb. 17, 1.942

. SUPERHETERODYNE RECEIVER t Johan Haantjes and Bernardus D. H.Tellegen,`

Eindhoven, Netherlands, yassignors to Radio Corporation of America, acorporation of Delaware Application June 14, 1940, Serial No. 340,500 Inthe Netherlands September 8, 1939 (Cl. 250m-20) 7 Claims.

,This invention relates to-superheterodyne receivers, particularly tothose in which at any one time the entire band of the oscillations tombe,received is admitted to the mixing Valve, as is the case for examplewith so-called infradyne sets. Thus, with these sets it is possible touse only a single tuning "circuit for the oscillator by making theintermediate frequency sufficiently high that is to say, beyond .thehighest; incoming frequency.

The present invention consists in that with such a receiver adiode isused as a mixing valve, and is based on `recognition of the fact thatthe use `of a diodek circuit for this purpose involves the use ofYautomatic preliminary selectivity with the result that the signals whichare instantaneously undesired yield a comparatively small voltage on'thedio'de so that cross modulation and howling noises are not troublesome.

In order that the invention may bey clearly lunderstood and readilycarried into effect it will now be described more fully with referenceto the accompanying drawing whereinlig. 1 shows a schematic of theinvention, Fig.,2 shows the frequency scale ofthe system, Fig. 3illustrates a -l receiver embodying the circuit of Fig. 1.

Fig. 1 is a well known mixing circuit in which lation's, an intermediatefrequency (I. F.) circuit If wi is` and a source of incomingoscillations. the frequency of the instantaneously desired station andwm the frequency to which the intermediate frequency ,circuit is tuned,the frequency wp of the oscillator must be chosen so that Now, theimpedance of such a circuit for frequencies adjacent wi is equal to thatof the parallel combination of a resistance R and a circuit tuned to wiwhose `impedance and absolute width are equal to those of theintermediate frequency circuit. If the resistance R of Fig. 1 is shuntedby the condenser C only in part, this substitution circuit is slightlyaltered but the tuned circuit remains.

If, therefore, in tuning the oscillator to wp a wide band of frequencieson either side of w1 is impressed on the circuit, the l-atter will havea much greater impedance for the desired frequency wr than for thehigher or lower frequencies so that automatic preliminary selectionresults.-

This latter fact is of considerable importance with the infradynecircuit.

t Fig. 2 shows a frequency dial scale of such an infradyne set. .Thefrequency range I comprised between wo and wg is that of the incomingoscillations. wm is the intermediate frequency. The range O comprisedbetween wm-i-wo and em-l-wg is that of the oscillator. The range Scomprised between Zwmi-wu-and 2wm+wg is that of the mirror frequencieswhich have to be suppressed. With the infradyne this suppression isgenerally effected by a low-pass lter. y

Fig. 3 shows` oneform of construction 'of an infradyne circuit accordingto the invention. The signal 4oscillations in an antenna A are suppliedto the input terminals of a low pass filter F. Between the outputterminals of 'this filter are connected in series the primary of anintermediate frequency transformer M, a diode D, a resistance R shuntedby a smoothing condenser C and an oscillator O. The lter F suppressesthe mirror frequencies, and the automatic preliminary selective natureof the remaining part of the circuit insures that cross modulation andhowling noises due to the stations undesired at that instant do notbecome troublesome. This latter effect may be assisted by selection of ahigher oscillator Voltage, and also by an improve- .oscillator providedwith means for tuning the `oscillator over a range of frequenciesdiffering from said carrier frequencies by an intermediate frequency,said intermediate frequency exceeding the highest carrier frequency ofsaid range, and an intermediate frequency circuit, said filter, os-

` cillator and intermediate circuit being connected in a closed seriescircuit with the electrodes of said mixer tube.

2. In combination with a diode mixer, a low pass wave input circuitconstructed to pass without selection all modulated carrier wavescomprised in a wide range, means impressing the waves passed by saidinput circuit upon said mixer, a local oscillator including means fortuning it to different desired frequencies comprised in a frequencyrange different from the carrier frequencies by a predeterminedintermediate frequency, said intermediate frequency being chosensubstantially higher than the highest carrier frequency of said inputrange, means comprising a resistor shunted by a condenser applying theoscillator output upon said mixer device, and an output circuitconnected to said mixer device tuned to said intermediate frequency.

3. In combination with a mixer device .of the electron discharge type, aWave input circuit con,- structed toy pass withoutV selection allmodulated carrier waves comprised in a wide range, means impressing theWaves passed by said input circuit upon said mixer, a local oscillatorincluding means for tuning it to diierent desired frequencies comprisedin a frequency range differing from the carrier frequencies byV apredetermined intermediate frequency, said intermediate fre-- quencybeing chosen substantially higher than the highest carrier frequency ofsaid input range, means applying the oscillator output upon said mixerdevice, and an output circuit connected to said mixer device tuned tosaid intermediate frequency, said mixer' device being a diode, and saidinput circuit being a low pass l-ter adapted to attenuate allfrequencies in excess ef said .highest carrier frequency. v

4. In combination with a mixer device of the electron discharge type, awave input circuit constructed to pass without selection all modulatedcarrier waves comprised in a wide range, means impressingv the wavespassed by said input circuit upon saidmixer, a local oscillatorincluding means for tuning it to different desired frequencies comprisedin a frequency range differing from. the carrier frequencies by apredetermined intermediate frequency, said intermediate frequency beingchosen substantially higher than the-highestcarrier frequency of saidinput range, means applying the oscillator output. upon said mixerdev-ice,l and an output circuit connected to saidmixer device. tuned tosaid intermedia-te fre- 5. In a superheterodyne receiver, an aperiodicsignal input network adapted to transmit solely the signal energycomprised in a wide band of signal carrier frequencies, a diode mixertube, means applying signal energy passed by said net- Work to saiddiode, a local oscillator connected to said diode, means for tuning theoscillator over a range of frequencies substantially higher than thehighest carrier of said band, and an output circuit connected to saiddiode which is tuned to a. frequency equal to the difference between thehighest carrier of said band and the frequency of said oscillator range.

6. In a superheterodyne receiver, an aperiodic signal input networkadapted to transmit solely the signal energy comprised in a wide band ofsignal carrier frequencies, a diode mixer tube, meansy applying signalenergy passed by said net- Work to said diode, a local oscillatorconnected to said diode, means for tuning the oscillator over arrange offrequencies substantially higher than the highest carrier of saidv band,a resistor in series With the space current path of the diode, acondenser in shunt with the resistor, and an output circuit connected tosaid diode which is tuned to a frequency equal to the diierence betweenthe highest carrier of said band and the frequency of said oscillatorrange.

7. Ina superheterodyne receiver, an aperiodic signal input networkadapted to transmit solely the signal energy comprised in a wide band ofsignal carrier frequencies, a diode mixer tube, means applying signalenergy passed by said net- Work to said diode, a local oscillatorconnected to-said diode, means for tuning the oscillator over a range.of frequencies substantially higher than the highest carrier of saidband, and an output circuit connected to said diode which is tuned to afrequency equal to the difference betweenv the highest carrier of saidband and the frequency of said oscillator range, said aperiodic network,output circuit and oscillator. all being in series relation with saiddiode.

JOHAN HAANTJES. BERNARDUS D. H. TELLEGEN.

